"After age 30, most men begin to experience a gradual decline in testosterone," says David Samadi, MD, chairman of the urology department at Lenox Hill Hospital in New York City.

Although testosterone levels never reach zero (as estrogen levels do in women during menopause), low testosterone levels men to experience symptoms such as fatigue, low libido, and loss of muscle mass.

While low testosterone is more prevalent in older men, it can occur in younger men as well. Luckily, all the causes of low testosterone in young men are curable, so in the event that you encounter such symptoms at any age, there is no reason to dismiss it.

Causes of Low Testosterone in Younger Men

For younger guys, a fall in testosterone levels can be caused by some ailments, such as type 2 diabetes, diabetes, chronic liver or kidney disease, COPD or other lung disease, or pituitary gland problems, according to Dr. Samadi.

Genetic causes of low testosterone in males include the diseases Klinefelter syndrome, Kallmann syndrome, Prader-Willi syndrome, and Myotonic dystrophy. Another disease which could cause low testosterone is hemochromatosis, which makes the body shop too much iron.

"Low testosterone can also result when something happens, like trauma or steroid use, that prevents the testes from making the hormone," states Bruce Gilbert, MD, PhD, an adjunct clinical professor of urology and reproductive medicine at Weill Cornell Medical College and director of reproductive and reproductive medicine at the Smith Institute for Urology of their North Shore-LIJ Health System.

Other causes of low testosterone in males younger than 50 contain adrenal gland tumors, HIV infection, and radiation therapy or chemotherapy for cancer.

Doctors categorize causes of low testosterone as secondary or primary.

"Primary hypogonadism stems from a problem in the testicles," Samadi says. In secondary hypogonadism, the testicles are normal but function improperly because of a problem with the hypothalamus or pituitary gland."

"When it comes to treating low testosterone in younger men, we generally reserve treatment for those who have symptoms, such as fatigue and low libido," Gilbert says.

Such testosterone supplements come in the form of a gel, injections, patches, long-acting pellets, or oral inserts.

In these circumstances,"therapies are often used just in the short term, and if a doctor has close observation and understanding of the patient," Gilbert says.

An important consideration for younger men before getting treatment is fertility. "You don't want to offer supplemental testosterone to men who want to be fertile since it can turn off sperm production," Gilbert says.

Once a young man goes off testosterone supplementation, there's a chance his sperm count will never return to what it was before he started. "Hence, men of reproductive age should think about alternatives which may increase their testosterone in addition to preserve their semen production," he says. One such alternative is a category of drugs called selective estrogen receptor modulators (SERMs).

Other remedies for low testosterone include weight loss and other lifestyle changes, like eating healthier and increasing exercise.

The main point, however, is that in the event that you've got low testosterone symptoms, then it's important to see your physician. Then, your doctor can rule out potentially more significant causes of your symptoms, including high blood pressure or a thyroid problem, and offer treatment that can improve your energy and quality of life.